Touch interface device having an electrostatic multitouch surface and method for controlling the device

ABSTRACT

A touch interface device includes a touch surface, a first electrode, and a second electrode. The first electrode is coupled with the touch surface. The first electrode also configured to receive a first haptic actuation electric potential. The second electrode is coupled with the touch surface. The second electrode also is configured to receive a different, second haptic actuation electric potential having an opposite polarity than the first haptic actuation potential. The first and second electrodes generate an electrostatic force that is imparted on one or more appendages of an operator that touches the touch surface above both the first electrode and the second electrode in order to generate a haptic effect.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit of U.S. Provisional ApplicationNo. 61/484,564, which also was filed on 10 May 2011 and is entitled “ATouch Interface Device Having An Electrostatic Multitouch Surface”(referred to herein as the “'564 Application”). This application isrelated to U.S. Provisional Application No. 61/484,544, which was filedon 10 May 2011 and is entitled “A Touch Interface Device Able To ApplyControllable Shear Forces To A Human Appendage” (referred to herein asthe “'544 Application”). This application also is related to U.S.application Ser. No. 13/468,695, which is filed concurrently with thepresent application and is entitled “A Touch Interface Device And MethodFor Applying Controllable Shear Forces To A Human Appendage” (referredto herein as the “'695 Application”). The entire disclosures of the '564Application, the '544 Application, and the '695 Application areincorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under grant numbersIIS0941581 and IIS0964075 awarded by the National Science Foundation.The government has certain rights in the invention.

BACKGROUND

Touch interface devices can include computing devices having displayscreens with touch sensitive surfaces that can be used to receive inputfrom operators of the devices. For example, many smart phones, tabletcomputers, and other devices having touch sensitive screens thatidentify touches from operators as input to the devices. Other examplesof touch interfaces can be found in laptop computers, gaming devices,automobile dashboards, kiosks, operating rooms, factories, automatictellers, and a host of portable devices such as cameras and phones.Touch interfaces can provide flexible interaction possibilities thatdiscrete controls do not.

“Haptics” refers to the perceptual system associated with touch. Hapticsallows people to touch type, find a light switch in the dark, wield aknife and fork, enjoy petting a dog or holding a spouse's hand. Hapticsis not just about moving one's hands, but includes perceptions such asfeeling things, recognizing objects (even without looking at theobjects), and controlling the way that people interact with the world.

Haptics in the form of vibration is a familiar feature of products suchas pagers, cell phones, and smart phones. Some known devices usevibration a silent ringer or alarm, and other devices use vibration toprovide feedback to the human hand (especially the fingertips) whenusing a touch screen. Some known touch interface devices usepiezoelectric actuators to vibrate just the display screen of the deviceso that the vibration is felt under the fingertips (e.g., on the screen)and less so or not at all in the hand holding the mobile device (e.g.,the vibration is not transmitted through the housing of the device).Such mechanical vibration can have certain drawbacks, such as relativelyhigh energy consumption. Furthermore, such mechanical vibration may notsupport multitouch, in which multiple fingertips simultaneously orconcurrently engage the display screen in more than one location. Forexample, in some known devices, the entire display screen or even theentire device vibrates. Because the entire screen or device vibrates,each fingertip touching the screen experiences the same effect. As aresult, the haptic effects provided to each fingertip cannot beindividually controlled (e.g., different from each other) at the sametime.

Some other known devices use electrostatic actuation to generatevibrations of the fingertips. These devices use electric fields to applyvibratory forces directly to the fingertips, and therefore do not haveany moving mechanical parts. The forces are highly localized anddifferent fingers may in principle experience different forces. Thesedevices, however, produce relatively small forces and can requirerelatively high voltages (e.g., 750-1000 volts). Moreover, because ofthe relatively small forces, the devices may be geared toward generatingperceived textures only.

What is needed is a system for producing relatively large forces so thatnot only textures and vibrations, but other effects including virtualbumps, virtual holes, collisions, virtual toggle switches, and the like,can be produced. A need also exists for practical and efficient ways toprovide different haptic effects to different fingertips at the sametime (e.g., multitouch effects).

BRIEF DESCRIPTION

In one embodiment, a touch interface device includes a touch surface, afirst electrode, and a second electrode. The “touch surface” of thedevice includes the top or exposed surface that is touched by anoperator. As described below, the touch surface can be an insulatinglayer that covers the electrodes that are coupled to a screen, surface,or other portion of the device. Alternatively, the touch surface can bethe exposed portion of the screen, surface, or other portion of thedevice, with the electrodes being disposed within the thickness of thetouch surface or coupled to a bottom or unexposed side of the touchsurface.

The first electrode is coupled with the touch surface and is configuredto receive a first haptic actuation electric potential. The secondelectrode is coupled with the touch surface and is configured to receivea different, second haptic actuation electric potential having anopposite polarity than the first haptic actuation potential. The firstand second electrodes generate an electrostatic force that is impartedon one or more appendages of an operator that touches the touch surfaceabove both the first electrode and the second electrode in order togenerate a haptic effect.

In another embodiment, another touch interface device includes a touchsurface and elongated electrodes coupled to the touch surface. Theelectrodes include a first electrode oriented along a first directionand a second electrode oriented along a different, second direction. Thefirst electrode extends over the second electrode at a firstintersection. The first and second electrodes are configured to receivehaptic actuation electric potentials of opposite polarities to generatean electrostatic force that is imparted on the one or more appendages ofthe operator that touch the touch surface above the first intersection.

In another embodiment, a method (e.g., for generating haptic effects ona touch surface of a touch interface device) includes applying a firsthaptic actuation electric potential having a first polarity to a firstelectrode coupled with a touch surface of a touch interface device. Themethod also includes applying a second haptic actuation electricpotential having a second polarity to a second electrode that is coupledwith the touch surface. The second polarity of the second hapticactuation potential is opposite of the first polarity of the firsthaptic actuation potential. The first and second haptic actuationpotentials generate an electrostatic force that is imparted on one ormore appendages of an operator that touch the touch surface above thefirst and second electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter described herein will be better understood fromreading the following description of non-limiting embodiments, withreference to the attached drawings, wherein below:

FIG. 1 is a perspective view of a touch interface device in accordancewith one embodiment;

FIG. 2 illustrates a model of an outermost layer of human skin of afingertip;

FIG. 3 illustrates another model of the outermost layer of human skin ofthe fingertip;

FIG. 4 is an electric circuit used to demonstrate a model of attractiveforces applied to a fingertip that engages a touch surface of theinterface device shown in FIG. 1;

FIG. 5 illustrates an impedance model of a system that includes thestratum corneum of the fingertip and an insulator shown in FIG. 4 inaccordance with one embodiment;

FIG. 6 is a diagram of a circuit of the system that includes the stratumcorneum, the insulator, and a conductor shown in FIG. 4 when the circuitdescribed above in FIG. 5 is closed through the capacitance of theoperator body (C_(b)) with respect to ground;

FIG. 7 is a circuit diagram of a circuit having a plurality ofconductors or electrodes in accordance with another embodiment;

FIG. 8 is another circuit diagram of a circuit having a plurality ofconductors or electrodes in accordance with another embodiment;

FIG. 9 is a schematic diagram of a lattice of electrodes in accordancewith one embodiment;

FIG. 10 is a schematic diagram of a touch interface device having alattice of electrodes in accordance with another embodiment;

FIG. 11 is a schematic diagram of a lattice of electrodes in accordancewith one embodiment;

FIG. 12 is a diagram of a circuit that models the circuit shown in FIGS.7 and 8 with a square wave voltage applied to one or more electrodes ofthe interface device shown in FIG. 1;

FIG. 13 illustrates a cross-sectional view of a portion of an exampletouch surface having multiple electrodes and insulating layers;

FIG. 14 illustrates an example of a circuit that can be used forsupplying different signals to a common electrode;

FIG. 15 illustrates one embodiment of electrodes used for timemultiplexing to provide both haptic effect and sensing functionalities;

FIG. 16 illustrates voltage-time curves that represent voltages appliedto the electrodes shown in FIG. 15 in accordance with one example;

FIG. 17 illustrates one example of determining a position of anappendage engaging a touch surface shown in FIG. 15 above an electrodealso shown in FIG. 15;

FIG. 18 illustrates an appendage of an operator engaging the touchsurface shown in FIG. 15 above several electrodes in a group ofelectrodes shown in FIG. 15 and an accompanying histogram representativeof electric charge sensed from the electrodes;

FIG. 19 illustrates a schematic diagram of a segmented electrode inaccordance with one embodiment; and

FIG. 20 is a flowchart of one embodiment of a method for generatinghaptic effects to one or more appendages that engage a touch surface ofa touch interface device.

DETAILED DESCRIPTION

In accordance with one or more embodiments described herein, severalapproaches for generating relatively large changes in normal forcesapplied to appendages of an operator of a touch interface device whenthe appendages engage a touch surface on a touch sensitive screen of thetouch interface device. The appendages are described herein asfingertips, but alternatively or additionally may include otherappendages, such as toes or even other body parts such as the palm.Changing these normal forces results in relatively large changes in thefrictional force between the fingertip and the touch surface of thetouch sensitive screen. The changes in normal forces can be implementedusing electrostatics. In one embodiment, to produce relatively largeforces, a voltage is applied to one or more conductors or electrodesdisposed below the touch surface and the voltage is modulated at afrequency. As used herein, the term “conductor” or “electrode” includesa conductive body to which an electric current, such as direct current,can be applied. The term “modulated” and various forms thereof includeschanging polarities of a voltage applied to the electrode, such as froma designated positive voltage to a designated negative voltage or fromthe negative voltage to the positive voltage. In one embodiment, thevoltage applied to the electrode is modulated at a frequency (referredto herein as a switching frequency) of at least 500 Hertz (500 Hz), andpreferably above 5 kiloHertz (5 kHz). For example, the voltage may bemodulated at a frequency of 50 kHz. In one embodiment, the voltage ismodulated at a frequency of at least 5 kHz. Such frequencies may be usedbecause the RC time constant of human skin may be relatively short sothat any electrostatic forces acting on the skin may dissipate in tensof microseconds.

It should be appreciated that the ability to modulate force on one ormore appendage is part of what makes haptic feedback via a touch surfacepossible. To create haptic experiences that are useful and/orinteresting, it is generally important to generate forces that closelycorrespond to specific actions of the fingertips and/or to specificevents occurring under software control. By way of illustration,consider a game in which the fingertips are used both to bat a ball, andto capture the ball. In this illustration, the ball is of course asimulated ball that appears on a computer display disposed underneaththe touch surface. Consider the act of batting the ball with one finger.In this case, the normal force generated by the methods described herewould depend on both the position and velocity of the finger as well asthe position and velocity of the simulated ball. Even higher derivativesof position, such as acceleration, might also be involved. In oneembodiment, the force exerted on the finger might increase when theposition of the finger intersects that of the surface of the ball,indicating a collision. The force might also depend on the relativevelocity of the finger and the ball, increasing for higher velocities.Thus we see that, unlike many existing technologies, the force is not asimple vibration that varies strictly as a function of time, but is africtional reaction force that varies as a function of state variablessuch as positions, velocities and accelerations. Now consider the act ofcapturing the ball and holding it between two fingers. In this case, thereaction forces at the two fingers, which are again functions of statevariables such as positions and velocities, should point inapproximately opposite directions. As the ball is held, the forcesshould persist. Thus we see that, unlike many existing technologies, theforce is neither a simple vibration nor even a transient. The abilitiesto generate persistent forces, and to generate different forces atdifferent fingers, are advantages of the technology described here. Inthe above discussion, it should be apparent that the technologydescribed here has been integrated with means of measuring the positionof one or more fingertips, and with means of displaying graphic images(and also audio, since events like batting a ball are often accompaniedby sound). There are many techniques for measuring fingertip positionswhich are known in the art, and which may be used here. These include,without limitation, resistive, surface capacitive, projected capacitive,infrared, acoustic pulse recognition, and in-cell optical sensing. Thereare also many techniques for displaying graphic images and audio.

Two or more sets of electrodes having different voltages applied to theelectrodes can be used to provide normal forces (and correspondingfrictional forces) to a fingertip (or other appendage) that engages thetouch surface of a touch interface device. The electric circuit thatincludes the electrodes and that is used to generate the forces can beclosed directly through the fingertip rather than through capacitance ofthe body of the operator of the device to the ground, or through anauxiliary ground contact. For example, a single fingertip may close thecircuit across two electrodes. Doing so can enable application of largernormal forces and may enable multitouch to be realized with aninterdigitated electrode pattern, as described below.

As described herein, an expression for the Coulomb (electrostatic)normal force on a finger is provided, and effects of “leakage” throughthe skin of the fingertip are added to this expression. A dynamic modelthat includes the effects of body capacitance is also provided. Thismathematical model helps the reader understand how one or moreembodiments of the presently described inventive subject matter canachieve higher forces imparted on fingetips than one or more knowndevices, and how multitouch feedback can be implemented. Specificapproaches to controlling force amplitude at multiple surface locationsare also provided.

In one embodiment, current levels that pass through the skin, due to thetouch interface device, may be below a level that creates directelectrical sensory stimulation. Instead, the normal force on thefingertip that is generated by the electrically charged electrodes canbe modulated, which in turn modulates frictional forces on thefingertip. Sensory stimulation to the fingertip may then occur whenthere is relative motion between the fingertip and the touch surface ofthe touch sensitive screen in the touch interface device. The sensationcomes from variations in friction at different times and/or locations onthe touch surface, and is therefore mechanosensory.

Localized regions of touch sensation may be provided on a touchinterface device for one or more fingers (referred to as contactpoints). For example, different normal forces and frictional forces maybe generated for different fingertips engaging different regions of thesame touch surface of the device.

The normal forces applied to the fingertips may be achieved usingrelatively low voltages, such as voltages below 750V rms. The normalforces may be generated by achieving relatively high electric fieldstrengths in the stratum corneum of the fingertip and insulator. Forthin insulators, sufficiently high field strengths may be achieved withmuch lower voltages, such as 10-100V rms.

In one embodiment, no auxiliary grounding is used with the touchinterface device. For example, a conductive strap or body that iscoupled with the device or with the operator of the device and a groundreference may not be used or needed. Instead, multiple electrodes in thedevice may be excited out of phase to create an electric circuit thatdoes not involve the capacitance of the operator's body to ground, noris a connection needed to the operator's body.

FIG. 1 is a perspective view of a touch interface device 10 inaccordance with one embodiment. The touch interface device 10 canrepresent a computing device, such as a smart phone, tablet computer,and the like. The touch interface device 10 includes a housing 16 havinga touch surface 12 (also referred to as a touch screen 12). The touchsurface 12 may be a touch-sensitive surface or display screen thatreceives input from an operator of the device 10 based on touch.Alternatively or additionally, the touch surface 12 may be anotherportion of the device 10 that does not display information (e.g.,images, text, videos, and the like) and/or that does not sense touch bythe operator. Although not shown in FIG. 1, the device 10 may include acontrol unit, such as a processor, controller, or other logic-baseddevice, that performs operations of the device 10 based on inputprovided by the operator touching the surface 12. While the discussionherein focuses on human fingertips engaging the touch surface 12,alternatively, one or more other human appendages (e.g., toes) may beused. One or more embodiments described herein provide ways to applyattractive forces on fingertips that touch the touch surface 12. Theattractive forces can provide haptic effects, such as perceived changesin the friction of the touch surface 12. For example, the attractiveforces can be oriented normal to the touch surface 12, as indicated bythe arrow 14. The attractive forces can be varied to change the frictionbetween the fingertip and the touch surface 12, thereby creating hapticeffects that are perceived by the operator.

FIGS. 2 and 3 illustrate models 200, 300 of an outermost layer 202 ofhuman skin of a fingertip 302, such as the layer that contacts the touchsurface 12 of the interface device 10 shown in FIG. 1. The outermostlayer 202 is referred to as the stratum corneum 204. The stratum corneumcontacts the external world. The stratum corneum includes of a layer ofdead cells that forms a moisture barrier. This layer is typically 20-40micrometers (μm) thick across much of the body, but can be considerablythicker on the soles of the feet and the fingertips. For the fingertips,the stratum corneum is typically 200-400 μm thick, varying with finger(thickest at the thumb), gender (thicker in men), and age.

The stratum corneum is the outermost layer of the skin and the outermostlayer of the epidermis. The mechanoreceptors responsible for touchsensation lie below the stratum corneum in the dermis 206. Of particularnote, the Pacinian corpuscles (which are responsible for vibrationdetection) lie well below in much more highly hydrated tissue.

FIG. 4 is an electric circuit 400 used to demonstrate a model ofattractive forces applied to a fingertip 302 (shown in FIG. 3) thatengages the touch surface 12 of the interface device 10 shown in FIG. 1.When the fingertip touches the touch surface 12, the human body mayserve as an electric ground reference 402. The stratum corneum 204(e.g., “finger” in FIG. 4) may serve as a dielectric layer between thebody ground and the outside world. An electrostatic device 404 may bemodeled as a electrode 410 that is covered by an insulator 412. Theelectrode 410 includes a conductor such as a conductive pad (whichshould be understood to include materials that are much less conductivethan metals) coupled to the touch surface 12. For example, the electrode410 can be disposed on the same side of the touch surface 12 that theoperator acts to touch and be covered by an insulative layer as theinsulator 412. Alternatively, the electrode 410 may be disposed belowthe surface 12 on a side of the surface 12 that is opposite of the sidethat the operator acts to touch. In another embodiment, the electrode410 may be disposed within the surface 12. An air gap 406 may or may notexist between the stratum corneum 204 and the insulator 412. At leastsome free charge (Q_(free) or Q_(f)) may be on a surface of theinsulator 412. The free charge may include charge that has leaked fromthe stratum corneum 204 (or through the air). In the circuit 400 shownin FIG. 4, the subscript sc refers to the stratum corneum 204, thesubscript g refers to the air gap 406, and the subscript i refers to theinsulator 412. The term ∈ refers to relative permittivity, d refers tothickness, and ρ refers to resistivity. Therefore, ∈_(sc) refers to therelative permittivity of the stratum corneum 204, ∈_(g) refers to therelative permittivity of the air gap 406, and ∈_(i) refers to therelative permittivity of the insulator 412, d_(sc) refers to thethickness of the stratum corneum 204, d_(g) refers to the thickness(e.g., size) of the air gap 406, d_(i) refers to the thickness of theinsulator 412, and ρ_(sc) refers to the resistivity of the stratumcorneum 204. Additionally, ∈_(o) refers to the relativity of free spaceand A refers to the area of the fingertip contacting the insulator.

A power source 408 can apply a potential difference, or voltage (V), tothe electrode 412 to generate an electric field between the electrode410 and the fingertip 302 (e.g., the stratum corneum 204). The electricfield extends across the insulator 404 and the air gap 406 to thefingertip 302 (e.g., stratum corneum 204). Several separate electrodes410 (e.g., electrodes that are not directly coupled with each other sothat the electrodes do not engage each other) can be coupled with thetouch surface 12, such as by being disposed on a first side of the touchsurface 12 that faces the operator during use of the device 10. Thetouch surface 12 of the device includes the top or exposed surface thatis touched by an operator. The touch surface can be an insulating layerthat covers the electrodes that are coupled to a screen, surface, orother portion of the device. Alternatively, the touch surface can be theexposed portion of the screen, surface, or other portion of the device,with the electrodes being disposed within the thickness of the touchsurface or coupled to a bottom or unexposed side of the touch surface.As used herein, the term “above” does not necessarily indicate arelative direction with respect to the ground or gravity. Given theseconditions, the electric field in each region of the touch surface 12can be computed from Gauss's Law and the relationship between theelectric field and a voltage or potential difference (V) applied to theelectrode 410 may be expressed as follows:

$\begin{matrix}{{{{- ɛ_{g}}E_{g}} + {ɛ_{i}E_{i}}} = \frac{Q_{free}}{ɛ_{o}A}} & \left( {{Equation}\mspace{14mu}{\# 1}} \right) \\{{{{- ɛ_{sc}}E_{sc}} + {ɛ_{g}E_{g}}} = 0} & \left( {{Equation}\mspace{14mu}{\# 2}} \right) \\{{{d_{sc}E_{sc}} + {d_{g}E_{g}} + {d_{i}E_{i}}} = {- V}} & \left( {{Equation}\mspace{14mu}{\# 3}} \right)\end{matrix}$

The electric field solutions (e.g., the electric fields generated in thestratum corneum 204, the air gap 406, and the insulator 412, or E_(sc),E_(g), and E_(i), respectively) can be expressed as:

$\begin{matrix}{E_{sc} = \frac{{- V} - \frac{Q_{f}}{C_{i}}}{d_{sc} + {\frac{ɛ_{sc}}{ɛ_{i}}d_{i}} + {\frac{ɛ_{sc}}{ɛ_{g}}d_{g}}}} & \left( {{Equation}\mspace{14mu}{\# 4}} \right) \\{E_{g} = \frac{{- V} - \frac{Q_{f}}{C_{i}}}{d_{g} + {\frac{ɛ_{g}}{ɛ_{i}}d_{i}} + {\frac{ɛ_{g}}{ɛ_{sc}}d_{sc}}}} & \left( {{Equation}\mspace{14mu}{\# 5}} \right) \\{E_{i} = \frac{{- V} + \frac{Q_{f}}{C_{g}} + \frac{Q_{f}}{C_{sc}}}{d_{i} + {\frac{ɛ_{i}}{ɛ_{sc}}d_{sc}} + {\frac{ɛ_{i}}{ɛ_{g}}d_{g}}}} & \left( {{Equation}\mspace{14mu}{\# 6}} \right)\end{matrix}$where the capacitances (e.g., the capacitance of the stratum corneum204, or C_(sc), the capacitance of the air gap 406, or C_(g), and thecapacitance of the insulator 412, or C_(i)) are defined as:

$\begin{matrix}{C_{sc} = \frac{ɛ_{sc}ɛ_{o}A}{d_{sc}}} & \left( {{Equation}\mspace{14mu}{\# 7}} \right) \\{C_{g} = \frac{ɛ_{g}ɛ_{o}A}{d_{g}}} & \left( {{Equation}\mspace{14mu}{\# 8}} \right) \\{C_{i} = \frac{ɛ_{i}ɛ_{o}A}{d_{i}}} & \left( {{Equation}\mspace{14mu}{\# 9}} \right)\end{matrix}$

A potential energy (U) that is stored in this system (e.g., thepotential energy stored in the stratum corneum 204, the air gap 406,and/or the insulator 412) can be expressed as:

$\begin{matrix}{U = {{\frac{1}{2}{C_{sc}\left( {E_{sc}d_{sc}} \right)}^{2}} + {\frac{1}{2}{C_{g}\left( {E_{g}d_{g}} \right)}^{2}} + {\frac{1}{2}{C_{i}\left( {E_{i}d_{i}} \right)}^{2}}}} & \left( {{Equation}\mspace{14mu}{\# 10}} \right)\end{matrix}$

A force (F_(sc)) that is imparted on the stratum corneum 204 byapplication of the voltage to the electrode 410 may be based on agradient of the potential energy (U) with respect to a change in thethickness of the air gap 406 (e.g., d_(g)) as follows:

$\begin{matrix}{F_{sc} = {- \frac{\partial U}{\partial d_{g}}}} & \left( {{Equation}\mspace{14mu}{\# 11}} \right) \\{F_{sc} = {{{- C_{sc}}E_{sc}d_{sc}^{2}\frac{\partial E_{sc}}{\partial d_{g}}} - {\frac{1}{2}\frac{\partial C_{g}}{\partial d_{g}}\left( {E_{g}d_{g}} \right)^{2}} - {C_{g}E_{g}{d_{g}\left( {E_{g} + {d_{g}\frac{\partial E_{g}}{\partial d_{g}}}} \right)}} - {C_{i}E_{i}d_{i}^{2}\frac{\partial E_{i}}{\partial d_{g}}}}} & \left( {{Equation}\mspace{14mu}{\# 12}} \right)\end{matrix}$

Rather than evaluate the general result, only the case as d_(g)→0 may beconsidered, such as when the finger is in contact with the insulator.The value of ∈_(g) may be 1, which can be appropriate for air. Theresult is:

$\begin{matrix}{F_{sc} = {\frac{ɛ_{i}d_{i}}{2\; d_{eq}^{2}}\left\lbrack {{C_{i}V^{2}} - \frac{Q_{free}^{2}}{C_{i}}} \right\rbrack}} & \left( {{Equation}\mspace{14mu}{\# 13}} \right) \\{{{where}\mspace{14mu} d_{eq}} = {d_{i} + {\frac{ɛ_{i}}{ɛ_{sc}}d_{sc}\mspace{14mu}(7)}}} & \left( {{Equation}\mspace{14mu}{\# 14}} \right)\end{matrix}$

In the case that Q_(free)=0, this expression can be rewritten as:

$\begin{matrix}{F_{sc} = \frac{ɛ_{o}{AV}^{2}}{2\left( {\frac{d_{sc}}{ɛ_{sc}} + \frac{d_{i}}{ɛ_{i}}} \right)^{2}}} & \left( {{Equation}\mspace{14mu}{\# 15}} \right)\end{matrix}$

Additionally, the following terms may be defined:

$\begin{matrix}{d_{i - {sc}} = {\frac{d_{sc}}{ɛ_{sc}} + \frac{d_{i}}{ɛ_{i}}}} & \left( {{Equation}\mspace{14mu}{\# 16}} \right) \\{C_{i - {sc}} = {\frac{C_{i}C_{sc}}{C_{i} + C_{sc}} = \frac{ɛ_{o}A}{d_{i - {sc}}}}} & \left( {{Equation}\mspace{14mu}{\# 17}} \right)\end{matrix}$so that the expression of force on the finger can be expressed as:

$\begin{matrix}{F_{sc} = \frac{C_{i - {sc}}V^{2}}{2\; d_{i - {sc}}}} & \left( {{Equation}\mspace{14mu}{\# 18}} \right)\end{matrix}$

The free charge (Q_(free)) can play an important role in the forcemodel. As Q_(free) grows, the force drops (e.g., Equations #13 and 14).The free charge can be due at least in part to the flow of currentthrough the stratum corneum 204 due to the non infinite resistivity ofthe stratum corneum 204, although the free charge could also accumulateslowly by the motion of ions through the air.

FIG. 5 illustrates an impedance model 500 of a system that includes thestratum corneum 204 and insulator 412 in accordance with one embodiment.The free charge (Q_(free)) may be the integral of the current that flowsthrough a resistor 502 (R_(sc)), which can represent the resistanceprovided by the stratum corneum 204. The stratum corneum 204 andinsulator 412 can be part of a larger dynamic system, the specifics ofwhich can depend on how the interface device 10 is built, and which caninclude a power source 504 (e.g., a battery). A basic model of thesystem may assume a single conductor (e.g., an electrode 410) under theinsulator 412 (e.g., the insulative or dielectric layer on the electrode410, at least a portion of the touch screen 12 of the device 10, and thelike) and no auxiliary grounding of the person using the device 10, orof the device 10 itself. The conductor 410 may have a significantresistance, especially if the conductor is made of or includes a lighttransmissive material such as Indium Tin Oxide (ITO). While thisresistance may be relevant when considering energy efficiency andheating, the resistance may be of less importance when consideringforces generated. For example, at the switching frequencies that may beused to supply electric energy to the conductor 410, the electricalimpedance of the system may be dominated by the capacitance of theoperator body and of the insulator 412 rather than the resistance of theconductor 410.

FIG. 6 is a diagram of a circuit 600 of the system that includes thestratum corneum 204, the insulator 412, and the conductor 410 when thecircuit described above in FIG. 5 is closed through the capacitance ofthe operator body (C_(b)) with respect to ground. Note that, in thisexample, it is assumed that the interface device has an Earth ground. Ingeneral, however, the interface device 10 may be floating relative toEarth ground (e.g., for a mobile device). In that case, C_(b) canrepresent the capacitance of the operator body with respect to theinterface device 10. The transfer function for the circuit 600 frominput voltage V_(o) to Q_(free) can be expressed as:

$\begin{matrix}{\frac{Q_{free}}{V_{o}} = {\frac{C_{i}C_{b}}{C_{i} + C_{b}}\frac{1}{{{R_{sc}\left( \frac{{C_{b}C_{sc}} + {C_{b}C_{i}} + {C_{i}C_{s\; c}}}{C_{b} + C_{i}} \right)}s} + 1}}} & \left( {{Equation}\mspace{14mu}{\# 18}} \right)\end{matrix}$

A time constant of this transfer function can be important. For example,at frequencies above the inverse of the time constant, the magnitude ofQ_(free) can become quite small, which may allow for larger forcesimparted on the fingertip touching the insulator 412 (e.g., the touchsurface 12 of the interface device 10) to develop.

The value for the capacitance of the whole human body with respect toground (C_(b)) may be 150 picoFarads (pF). If the insulator 412 has arelative permittivity of ∈_(i)=5, which may be typical for glass andmany plastics, and the area of engagement between the fingertip and theinsulator 412 is approximately 1 cm², then C_(i)=442 pF. The valuesassociated with fingertip may depend on moisture content of the skin.Some examples of resistivity and relative permittivity values for thefingertip include:

-   -   (a) Dry skin at a switching frequency of 10 kiloHertz (kHz):        ρ_(sc)=5000 Ohm-meters (Ωm), ∈_(sc)=1,133    -   (b) Wet skin at a switching frequency of 10 kHz: ρ_(sc)=333 Ωm,        ∈_(sc)=29,000        where the switching frequency represents the frequency at which        the polarity of the voltage applied to the conductor 412 is        switched. With the area assumption above and a stratum corneum        thickness of 200 μm, the resistance and capacitance of the        fingertip may be:    -   (a) Dry skin at 10 kHz: R_(sc)=10 kΩ, C_(sc)=5 nanoFarads (nF)    -   (b) Wet skin at 10 kHz: R_(sc)=667Ω, C_(sc)=128 nF

Using the above values to compute the system time constant (τ), the timeconstant is calculated to be as follows, although other time constantscould result from other conditions:

-   -   (a) Dry skin: τ_(system)=51 microseconds (μs) (3.1 kHz)    -   (b) Wet skin: τ_(system)=86 μs (1.9 kHz)

To achieve relatively strong normal forces applied to the finger, in oneembodiment, the switching frequency or excitation frequency (e.g., thefrequency at which the polarity of voltage applied to theconductor/electrode 412 is switched) is approximately 3 times thefrequency implied by the above time constants. At excitation frequenciesof 5-6 kHz and above, the effects of the free charge may be reduced andcan even become negligible. As a result, the force applied to the fingercan depend primarily on the voltage V acting across the stratum corneum204 and the insulator 410 from the conductor/electrode 412. The transferfunction from input voltage V_(o) to V, where the input voltage is thevoltage applied to the conductor/electrode, can be expressed as:

$\begin{matrix}{\frac{V}{V_{o}} = {\frac{C_{b}}{C_{i} + C_{b}}\frac{{{R_{sc}\left( {C_{sc} + C_{i}} \right)}s} + 1}{{{R_{sc}\left( \frac{{C_{b}C_{sc}} + {C_{b}C_{i}} + {C_{i}C_{sc}}}{C_{\; b} + C_{i}} \right)}s} + 1}}} & \left( {{Equation}\mspace{14mu}{\# 19}} \right)\end{matrix}$

The zero occurs at a lower frequency than the pole; thus, if the sameassumption of operating above 1/τ_(system), the force may be computedas:

$\begin{matrix}{F_{sc} = {\left( {1 + \frac{C_{i - {sc}}}{C_{b}}} \right)^{- 2}\frac{C_{i - {sc}}V_{o}^{2}}{2\; d_{i - {sc}}}}} & \left( {{Equation}\mspace{14mu}{\# 20}} \right)\end{matrix}$

This Equation 20 may be compared to Equation 18. The term that is addedto Equation 20 represents the effect of the operator body's capacitance,which can be quite significant. Using the parameters above, and assumingdry skin, the added factor has a value of 0.073. For example, the forceon the fingertip can be attenuated by a factor of 0.073.

One or more of the values in term

$\left( {1 + \frac{C_{i - {sc}}}{C_{b}}} \right)^{- 2}$of Equation 20 can be examined to increase the force applied to thefingertip. In one embodiment, the capacitance of the operator's body(C_(b)) can be increased. For example, the operator may hold onto aground strap, or a conductor that is coupled with a ground reference,when the operator's fingertip engages the touch surface. Of particularnote, an array of ground electrodes may be disposed on the top of thetouch surface 12 such that a small portion of the finger's contact patchis always grounded while the majority of the contact patch iscapacitively coupled to a high-voltage electrode. For handheld devicessuch as mobile phones or tablet computers, the concept of ground, groundreference, ground electrodes, and ground strap may refer to the localground of the device 10, rather than referring to Earth ground. In someembodiments, the function of a ground strap may be obtained by theoperator making electrical contact with the device 10, for examplethrough a conductive case (e.g., the housing 10) or back of the device12, or even such a case or back with a insulating layer thatnevertheless allows an elevated value of C_(b). Similarly it should beunderstood that the potential of the local ground of the device 10 maybear an arbitrary relationship to potential of earth ground.Alternatively, the electrical circuit 600 may be modified such that thebody's capacitance C_(b) plays a much reduced role.

FIGS. 7 and 8 are circuit diagrams of a circuit 700 having a pluralityof conductors or electrodes 702, 704 in accordance with anotherembodiment. In contrast to the circuits described above having a singleelectrode 412 beneath the fingertip, the circuit 700 includes aplurality of electrodes 702, 704 beneath the fingertip. The electrodes702, 704 may be supplied by a power source 706 with equal and oppositevoltages (−V₀, +V₀), or with voltages substantially different from eachother even if not equal and opposite. A change of ground reference canbe arbitrary and may not affect the electrostatic forces. The potentialsdescribed herein are potentials relative to a convenient ground. Thetissue underneath the stratum corneum 204 of the fingertip is relativelyconductive and can complete the circuit 700 and reduce the relevance ofor make irrelevant the capacitance of the operator's body (C_(b)) in thecircuit 700. The switching frequency at which the voltages supplied tothe electrodes 702, 704 changes polarity may be sufficiently high thatcharge leakage is significantly reduced and may be ignored. In FIG. 8,C_(p) represents parasitic capacitance between the electrodes 702, 704and α represents a ratio of the portions of the areas of the electrodes702, 704 that are underneath the fingertip contact area A (e.g., thearea that the finger contacts the touch surface 12). The force appliedto the fingertip obtained with such a circuit 700 may be represented as:

$\begin{matrix}{F_{sc} = \frac{\alpha\; C_{i - {sc}}V_{o}^{2}}{d_{i - {sc}}}} & \left( {{Equation}\mspace{14mu}{\# 21}} \right)\end{matrix}$

The attenuation term

$\left( {1 + \frac{C_{i - {sc}}}{C_{b}}} \right)^{- 2}$from Equation 20 is not present in Equation 21, and the only loss versusEquation 17 is geometrical due to loss of the electrode area (e.g.,α<0.5). The parasitic capacitance C_(p) may not affect the force or mayhave a reduced impact on the force exerted on the fingertip, but mayincrease current drawn from the power supply 706 and lead to increasedresistive losses. In one embodiment, the parasitic capacitance C_(p)should be relatively small, such as on the order of 5 pF.

In addition to circuit 600, Equation 21 demonstrates that d_(i-sc) canbe reduced in order to increase the force level. The value of d_(i-sc)depends on both the stratum corneum, which may not be altered, and theinsulator layer 412, which can be. In practice, the electricalthickness, d_(i)/∈_(i), of the insulator layer 412 can be reduced bydecreasing the physical thickness of the insulator layer 412 (e.g., thethickness d_(i)) and/or increasing the dielectric constant ∈_(i). Forinstance, in one embodiment, the insulator layer 412 may be a 1 micronthick layer of Hafnium Oxide (HfO₂). HfO₂ has a relatively highdielectric constant (˜25) as well as good breakdown strength. Many othermaterials may be chosen as well. For instance, silica, Titanium Oxide,Barium Titanate, and various polymers, such as parylene.

As the top layer of the device 10, the insulator layer 412 also may beresponsible for meeting other requirements, such as opticaltransmission, anti-reflection, providing a moisture barrier, providinghydrophobic and oleophobic properties, and the like. Toward this end,various surface treatments and coatings may be applied to the insulatorlayer 412 without significantly affecting the electrical properties(e.g., d_(i) and ∈_(i)). The surface of the insulator layer 412 may alsobe textured using techniques such as acid etching. Texture may reducereflections and provide more consistent frictional properties withoutaffecting electrical characteristics.

The attentuation term from Equation 20 may be added back into thecalculation of the force imparted on the fingertip when the electrodes702, 704 are driven with the same voltage polarity, or when only oneelectrode 702 or 704 is driven (e.g., receives voltage) and the otherelectrode 704 or 702 is allowed to float relative to ground. In thelatter case, the force may be expressed as:

$\begin{matrix}{F_{sc} = {{\alpha\left( {1 + \frac{C_{i - {sc}}}{C_{b}}} \right)}^{- 2}\frac{C_{i - {sc}}V_{o}^{2}}{2\; d_{i - {sc}}}}} & \left( {{Equation}\mspace{14mu}{\# 22}} \right)\end{matrix}$

The difference between the forces calculated by Equations 21 and 22 canbe used to create localized haptic effects while also reducing thenumber of electrodes 702, 704 that are used to create the hapticeffects.

FIG. 9 is a schematic diagram of a lattice 800 of electrodes 802, 804(e.g., electrodes 802A-F and electrodes 804A-F) in accordance with oneembodiment. The electrodes 802, 804 are elongated conductive bodies thatare oriented along perpendicular x- and y-axes 810, 812, respectively.As shown in FIG. 9, the electrodes 804 are disposed above the electrodes802 such that the electrodes 802, 804 are not conductively coupled witheach other and the electrodes 802, 804 can be separately supplied withcurrent. For example, the electrodes 802, 804 may be conductivelyseparated from each other in areas where the electrodes 802, 804 crosseach other such that no conductive pathway exists between the electrodes802, 804 that cross each other. A dielectric or insulating layer may beprovided between the electrodes 802, 804 to prevent the electrodes 802,804 from being conductively coupled. Alternatively or additionally, theelectrodes 802, 804 may be vertically spaced apart from each other suchthat the electrodes 802, 804 are not conductively coupled.

The lattice 800 may be disposed below the insulative touch surface 12 ofthe touch interface device 10. Alternatively, the lattice 800 may bedisposed on the same side of the touch surface 12 that is touched by anoperator of the device 10. In another embodiment, the lattice 800 may belocated within the thickness of the touch surface 12. The electrodes802, 804 include conductively interconnected diamond shaped pads 806.Alternatively, the pads 806 may have a different shape. The diamondshape of the pads 806 may allow multiple electrodes 802, 804 to beexcited simultaneously while reducing stray capacitance. The pads 806 inthe same electrode 802 or 804 are conductively coupled with each otherby conductive bridges 814.

In the illustrated embodiment, the electrodes 802C and 804B (onevertical electrode and one horizontal electrode) are activated while theother electrodes 802, 804 are not activated (or are activated but onlyto an lesser voltage.) When a fingertip is placed above an intersection808 of the activated electrodes 802C, 804B (e.g., the location where theelectrode 804B extends over the electrode 802C), the force applied toattract the fingertip toward the electrodes 802C, 804B is represented byEquation 21, and may be relatively large. As a result, the operator mayfeel his or her finger pulled toward the touch surface 12 of the device10. When the fingertip is placed elsewhere along the length of eitherelectrode 802C or 804B and away from the intersection 808, the forceapplied to pull the finger toward the touch surface 12 may berepresented by Equation 22, and may be reduced relative to the forceapplied when the finger is above the intersection 808.

If the lattice 800 includes M electrodes 804 disposed side-by-side alongthe x axis 810 and N electrodes 802 disposed side-by-side along the yaxis 812 (e.g., where M and N represent integer numbers that may be thesame number or different numbers), then the number of individual regionsof the touch surface 12 that may be separately addressed (e.g., applyvoltage to) in this manner is M×N. For example, a total of M×N regionsof the lattice 800 on, below, or within the touch surface 12 may haveboth a horizontal electrode 802 and a vertical electrode 804 excitedwithin the region. The ability to address M×N regions with hapticoutputs while only having M+N electrodes 802, 804 may represent asignificant savings in complexity of the interface device 12.

FIG. 10 is a schematic diagram of a touch interface device 900 having alattice 902 of electrodes 904, 906 in accordance with anotherembodiment. The interface device 900 may be similar to the device 10shown in FIG. 1. The lattice 902 of electrodes 904, 906 may bepositioned on, below, or within a touch surface of the device 900, suchas the surface 12 of the device 10. The lattice 902 provides anarrangement of pairs 908 of the electrodes 904, 906 that can beactivated to provide multiple regions of forces. For example, theelectrodes 904, 906 in different pairs 908 may be simultaneously orconcurrently activated (e.g., supplied with voltage) to provide forceson different fingertips touching different portions of the touch screenof the device 900 at the same time.

FIG. 11 is a schematic diagram of a lattice 1000 of electrodes 1002,1004 (e.g., electrodes 1002A-F and electrodes 1004A-F) in accordancewith one embodiment. Similar to the electrodes 802, 804 (shown in FIG.9) and/or 904, 906 (shown in FIG. 10), the electrodes 1002, 1004 may bepositioned on, below, or within the touch surface 12 of the device 10.The electrodes 1002, 1004 are elongated conductive bodies that areoriented along perpendicular x- and y-axes 1008, 1010, respectively. Asshown in FIG. 11, the electrodes 1004 extend over the electrodes 1002such that the electrodes 1002, 1004 are not conductively coupled witheach other and the electrodes 1002, 1004 can be separately supplied withcurrent, similar to as described above in connection with the electrodes802, 804.

If specific and/or different forces are desired at a first intersection1006 of a first set of the electrodes 1002D, 1004B and at a different,second intersection 1008 of a different, second set of the electrodes1002A, 1004E, the first set of the electrodes 1002D, 1004B can beexcited with voltage and the second set of the electrodes 1002D, 1004Balso can be excited with voltage from a power source. In one embodiment,the voltage applied to the sets of electrodes 1002, 1004 at eachintersection 1006, 1008 can be phased differently. For example, thevoltage applied to the electrode 1002D may be expressed asV_(1002D)=sin(ωt+φ) and the voltage applied to the electrode 1004B maybe expressed as V_(1004B)=sin(ωt). Similarly, the voltage applied to theelectrode 1002A may be expressed as V_(1002A)=sin(ωt+φ) and the voltageapplied to the electrode 1004E may be expressed as V_(1004E)=sin(ωt).

Forces that attract fingertips toward the touch surface 12 also may begenerated all along lengths of each active electrode 1002A, 1002D,1004B, 1004E, but such forces may be relatively small compared to theforces applied to fingertips when fingertips are at either or both ofthe intersections 1006, 1008. If there is only a single fingertip placedat one of the intersections 1006 or 1008, but not both, it is stillpossible to control the force applied to the fingertip by setting onemore phase angle; e.g., the phase of the electrode 1002A relative to thephase of the electrode 1004E.

When fingertips are placed at all four intersections—for example, atfour locations that form a rectangle aligned with the electrodes 1002,1004E, 1002D, 1004B—it may still be possible to generate compellinghaptic effects, but the forces may need to be coordinated. For instance,it may be not undesirable that the forces at two of the fingers beconstrained to be equal.

The forces applied to different fingertips that concurrently orsimultaneously touch the touch surface 12 can be individuallycontrolled. For example, a first force applied to a first fingertipengaging a first region of the touch surface 12 may be different (e.g.,greater) than a second force applied to a different, second fingertipengaging a different, second region of the touch surface 12. Forexample, given sinusoidal voltages applied to the electrodes with afrequency greater than 1/τ_(system) and an amplitude V_(o), Equations 21and 22 described above may represent potential extremes of the forces(e.g., maximum and minimum, or upper and lower) that are possible withthe two-electrode configurations shown in one or more of FIGS. 9 through11. Alternatively, Equation 21 and/or 22 may represent one or moreforces applied to the fingertips that are not the maximum and minimum,but forces between the potential maximum and minimum forces.

The forces applied to one or more of the fingertips may be variedbetween the values expressed in Equation 21 and/or 22. For example, theamplitude of the voltage (V_(o)) applied to one or more of theelectrodes may be changed to change the forces. As another example, aphase difference (Φ) between the voltages applied to the two electrodesmay be altered to change the forces. In one embodiment, the forceapplied to one or more fingertips may be increased when the phasedifference (Φ) in the voltages applied to the two electrodes is 180degrees. Conversely, the force applied to one or more fingertips may bedecreased when the phase difference (Φ) is 0 degrees. Differences in thephase between 0 degrees and 180 degrees may scale the force accordingly.

In one embodiment, the voltages applied to the electrodes may be appliedin sinusoidal profiles or waveforms. Alternatively, the voltages may beapplied in square waveforms. Other waveforms may also be used.

FIG. 12 is a diagram of a circuit 1100 that models the circuit 700 shownin FIGS. 7 and 8 with a square wave voltage applied to one or moreelectrodes of the interface device 12 described herein. The square wavevoltages applied to the electrodes is represented by switches 1102,1104. For example, when a positive polarity voltage is applied to afirst electrode, the switch 1102 couples the positive voltage (+V₀) withthe first electrode and when a negative polarity voltage is applied tothe first electrode, the switch 1102 couples the negative voltage (−V₀)with the first electrode. Similarly, when a positive polarity voltage isapplied to a different, second electrode, the switch 1104 couples thepositive voltage (+V₀) with the second electrode and when a negativepolarity voltage is applied to the second electrode, the switch 1102couples the negative voltage (−V₀) with the second electrode. Theswitches 1102, 1104 may be coordinated with each other such that whenthe positive voltage (+V₀) is applied to the first or second electrode,the negative voltage (−V₀) is applied to the other second or firstelectrode, and vice-versa. As noted previously the ground reference canbe arbitrary. The voltage magnitudes applied to the electrodes may beequal, positive and negative, or may differ from each other.

The forces applied to fingertips by the different electrodes may bevaried. For example, the frequency at which the voltage applied to oneor more of the electrodes is switched between polarities may be alteredto control the applied force. In one embodiment, at frequencies below afrequency of 1/τ_(system), the force may increase with increasingfrequency. For example, the force may linearly grow with increasingfrequency.

In another embodiment, the width of the voltage pulses applied to theelectrodes may be modulated. For example, the voltages may be applied ina plurality of states, such as a “high force state” and a “low forcestate.” The high force state may occur when two electrodes are connectedto opposite rails (e.g., the electrodes receive opposite polarities ofthe voltage) and the low force state may occur when the electrodes areconnected to the same rail (e.g., the electrodes receive the samepolarity of voltage). A “pulse” of the voltage may represent a time (α)Tthat the electrodes are in the high force state followed by a time(1−α)T that the electrodes are in the low force state. The variable acontrols or represents an average force amplitude. In one embodiment, toincrease the range of forces that can be applied by the electrodes, thevalue of T may be less than τ_(system).

In another embodiment, the switches 1102, 1104 may be alternated betweenthe positive and negative polarities of voltage at a fixed rate, butwith a controllable phase difference in order to control the amplitudeof the forces applied by the electrodes.

In another embodiment, the number of pulses of voltage applied to theelectrodes may be modulated to vary the amplitude of the forces appliedby the electrodes. For example, if several pulses of voltage are appliedin a 50 kHz pulse train, a set of 50 voltage pulses may repeat at 1 kHz,which is above the bandwidth of tactile perception of a human operator.The forces may be modulated by turning off or on some of the pulses inthe set of 50. For example, if 40 pulses are on and 10 pulses are off,the force applied may be 80% of a potential peak value. This may besimilar to frequency modulation, but the fundamental can remain at 50kHz. Alternatively, one might choose to repeat sets of voltage pulses ata frequency below 1 kHz, for instance at 300 Hz, which would produce asensation of vibration for the human operator. It should be evident thata great variety of haptic effects can be created through frictionmodulation, and these effects may derive from patterns of activationwhich are not perceived as vibration, combined with patterns ofactivation which are perceived as vibration.

As described above, finger position sensing on a touch surface 12 may beperformed using conductive layers (e.g., electrodes 410, 702, 704, 802,804, 904, 906, 1002, 1004) below an insulating layer (e.g., insulator412), to measure the location of the finger or fingers of an operator onthe touch surface 12. These conductive layers can be patterned so thatmultiple electrically isolated regions are present, such as describedabove in connection with FIGS. 9 through 11. As described above,conductive bridges or jumpers may be used to conductively couplephysically non-contiguous conducting regions (e.g., pads 806), such asshown in and described in connection with FIG. 9. There can be more thanone conductive layer, separated by insulating layers, to form analternating vertical sequence (with respect to a direction that extendsbetween an appendage of an operator and the touch surface 12) ofelectrodes.

FIG. 13 illustrates a cross-sectional view of a portion of an exampletouch surface 1300 having multiple electrodes 1302, 1304 and insulatinglayers 1306, 1308. The surface 1300 may be similar to the touch surface12 of the device 10 described above. For example, the surface 1300 maybe capable of perceiving touch from an operator and of generating hapticeffects that are perceived by the operator. The device 1300 includes themultiple electrodes 1302, 1304 and insulating layers 1306, 1308 stackedon top one another and coupled with a screen 1310, such as a displayscreen or other surface of the device 10.

The electrodes 1302, 1304 may be used for sensing touch of the device 10that includes the surface 1300 and/or for generating haptic effects, asdescribed herein. As shown in FIG. 13, the electrodes and insulatinglayers are disposed on a side of the device that an operator acts totouch. As described herein, the operator touching or acting to touch thesurface 1300 may involve the operator touching the insulating layer 1308instead of actually engaging the underlying screen 1310. The electrodesand insulating layers may be at least partially transparent, or lighttransmissive, so that a visual display can be seen through the touchscreen 1300 by the operator, as described above. One transparent andelectrically conductive material that can used for such layers is IndiumTin Oxide, ITO.

As described above, one or more embodiments of the inventive subjectmatter described herein generates haptic effects using a conductivelayer beneath an insulating layer. The conductive layer may bepatterned. In one embodiment, the same conductive layers may be used toboth sense the position of the appendages of the operator and to displayor produce haptic effects that are felt by the appendages. Sincepatterned conductive layers and insulating layers can be used in fingerposition sensing, and since patterned conductive layers and insulatinglayers can be used in creating haptic effects, it can be desirable to beable to use the same layer or layers for both of these functions. Evenif different conducting and/or insulating layers are used for thefunctions of sensing position of the appendages of the operator and ofproviding haptic effects, it can be desirable that the differentconductive layers not interfere with each other. Interference can belikely due to the relatively strong capacitive coupling of theconductive layers that are separated by relatively small distances.

Whether the conductive layers (e.g., electrodes) used for sensing andhaptics are the same or different conductive layers, the functions havea propensity to interfere with each other. That is because, in oneembodiment, both sensing and haptic actuation use AC voltages suppliedto the conductive layers. The haptic actuation of the conductive layersmay use larger voltages while the sensing function of the conductivelayer uses smaller voltages. As a result, the haptic actuation is likelyto interfere with the sensing function more than the sensing functioninterfering with haptic actuation. The interference is likely even ifthe conductive layer or layers are divided across the surface 12 betweenthe two functions, because of the capacitive coupling between parts ofthe conductive layers.

To allow a finger position sensing function to go on undisturbed byhaptic actuation on the same or a different conductive layer, or toreduce the interference caused by haptic actuation, the functions may beseparated by having the functions operate at different frequencies(e.g., by controlling the frequencies at which electric current issupplied to the conductive layer for the different functions) and/or bytime multiplexing the functions (e.g., by temporally controlling whenthe conductive layer is supplied with electric current to provide eachfunction).

To separate the functions by frequency, one function (e.g., providinghaptic effects or sensing touch) is performed at a different frequencyor frequency range than another function. For example, haptic actuationof the conductive layers or electrodes may occur at a lower frequency orfrequencies than the frequency or frequencies used for sensing touch.Alternatively, haptic actuation may be performed at a larger frequencyor frequencies than sensing. In one embodiment, haptic actuation of theconductive layers or electrodes is performed at frequencies of 101 KHzor less, although other, considerably lower or higher frequencies can beused. Capacitive sensing of the conductive layers or electrodes may beperformed at frequencies of is 5 MHz or greater, although higher orlower frequencies can also be used. Voltages that are applied to theconductive layers for capacitive sensing may be smaller than thevoltages applied to the conductive layers for creating the hapticeffects. For example, the voltages used for sensing may be on the orderof a few volts, such as 3.3 volts or 5 volts, or another voltage, whilelarger voltages may be applied for generating haptic effects. Therelatively smaller voltage and higher frequency signal that is appliedto the conductive layer for sensing touch can be superimposed on thelarger voltage and lower frequency signal that is applied to theconductive layer for haptic actuation. The high frequency signal usedfor sensing touch can be stripped out again from the conductive layerfor interpretation by using a high pass filter.

FIG. 14 illustrates an example of a circuit 1400 that can be used forsupplying different signals 1402, 1404 to a common electrode 1406. Thecircuit 1400 can supply the signals 1402, 1404 to activate the electrode1406 for both sensing and haptic effect functionality. The electrode1406 may represent one or more of the electrodes described above. Thecircuit 1400 may entirely or partially be disposed within one or more ofthe touch interface devices described herein.

The signal 1402 may represent a haptic activation signal that issupplied from one or more power sources of the touch interface deviceand can include an electric current having a first voltage and a firstfrequency. The signal 1402 is supplied to the electrode 1406 to createthe haptic effects described herein. The signal 1404 may represent asensing signal that is supplied from one or more power sources of thetouch interface device and can include an electric current having alower, second voltage and a larger, second frequency relative to thefirst voltage and first frequency of the signal 1402. In one embodiment,the first voltage of the haptic activation signal 1402 is 50 volts andthe second voltage of the sensing signal 1404 is 5 volts. Alternatively,one or more other voltages may be used. The first frequency of thehaptic activation signal 1402 may be 10 KHz while the second frequencyof the sensing signal 1404 is 5 MHz, although one or more otherfrequencies may be used in another embodiment.

The signals 1402, 1404 may be supplied to an interface device 1408 thatis conductively coupled with the electrode 1406. The interface device1408 can include one or more components that superimpose, mix,interleave, sum, or otherwise concurrently or simultaneously place bothsignals 1402, 1404 on the same electrode 1406. For example, theinterface device 1408 may represent a mixer, summer, modulator, or thelike. The haptic activation signal 1402 can drive the electrode 1406 toprovide haptic effects described above while the sensing signal 1404 maybe used to sense touch by an operator. The sensing signal 1404 on theelectrode 1406 can be monitored to detect touch by coupling theelectrode 1406 with a filter 1410, such as a high pass filter, thatstrips out the sensing signal 1404 from the current on the electrode1406. The stripped out sensing signal 1404 may then be communicated to acontrol unit 1412 that examines the sensing signal 1404 to determine ifan operator has touched the insulating layer disposed above theelectrode 1406. The control unit 1412 can include one or moreprocessors, microcontrollers, and the like, that operate based onhard-wired and/or software instructions to carry out one or moreoperations. In one embodiment, the control unit 1412 may direct theapplication or supply of current to electrodes of a touch interfacedevice, such as by controlling the application of the signals 1402, 1404to the electrode 1406. Other touch interface devices described hereinmay include the same or similar control units to control the supply ofelectric current to the respective electrodes.

In another embodiment, to separate activation of an electrode forproducing haptic effects and for sensing touch using time multiplexing,the capacitive sensing performed by the electrode is interleaved withrespect to time with haptic actuation of the electrode.

FIG. 15 illustrates one embodiment of electrodes 1500 (e.g., electrodes1500A-D) used for time multiplexing to provide both haptic effect andsensing functionalities. The electrodes 1500 may be positioned on ascreen or surface of the touch interface device 10, such as by placingthe electrodes 1500 on or within a screen to provide the touch surface12. In one embodiment, the electrodes 1500 are formed by patterning asingle layer of ITO (or another material).

The single ITO layer (or other conductive layer) can be used for bothhaptic actuation and finger position sensing. The layer is patternedinto parallel stripes (e.g., to form the electrodes 1500) separated bynon-conducting separation gutters 1502 (e.g., gutters 1502A-C). In oneembodiment, the electrodes 1500 may be 3/16 inches (or 4.8 mm) wide andthe gutters 1502 may be 100 μm wide. Alternatively, another dimensionmay be used for the width of the electrodes 1500 and/or gutters 1502.The electrodes 1500 may be created by laser ablation of a conductivelayer, such as a layer of ITO. Each stripe of electrode 1500 can beelectrically accessible at each of opposite ends 1504, 1506. At leastpart of the electrodes 1500 may be covered with an insulating materiallayer 1508, such as SiO₂, HfO₂, or another material, over most of atouch sensitive area 1510 of the electrodes 1500 between the ends 1504,1506 where the electrodes 1500 are to be touched. Given a typicalconductivity of transparent ITO, the end-to-end resistance of eachelectrode stripe 1500 (e.g., between the ends 1504, 1506) can be on theorder of 1000 ohms, depending on the thickness and conductivity of theelectrode 1500, the length of the electrode 1500 between the ends 1504,1506, the width of the electrodes 1500, and the like. Alternatively,each electrode 1500 may have another resistance.

Haptic actuation of the stripe electrodes 1500 may be performed byclassifying or logically associating each electrode 1500 into one of twoor more groups. For example, the electrodes 1500 can be classed into twotypes, A and B, with alternate electrodes 1500 being of each class, sothe order of the electrodes 1500 is ABABAB. In the illustratedembodiment, the electrode 1500A may be in the A group or class, theelectrode 1500B may be in the B group or class, the electrode 1500C maybe in the A group or class, the electrode 1500D may be in the B group orclass, and so on. Current is supplied to the electrodes 1500 for hapticactuation, as described above. The polarity of the voltage applied tothe electrodes 1500 in the different groups or classes may be switchedat a frequency. For example, the polarity of the voltage applied to theelectrodes 1500 can be reversed every 50 μs (or another time period).During a switch from a first time period to a subsequent second timeperiod, the electrodes 1500 in the A group or class may change from apositive voltage to a negative voltage and the electrodes 1500 in the Bgroup or class may switch from a negative voltage to a positive voltage.During the subsequent switch from the second time period to a laterthird time period, the electrodes 1500 in the A group or class mayswitch from the negative voltage to the positive voltage while theelectrodes in the B group or class switch from the positive voltage tothe negative voltage. The voltage that is applied to the electrodes 1500can be varied depending on the haptic effect desired. In one example, tocreate a temporal pattern at 50 Hz, the voltage applied to theelectrodes 1500 can be 45 volts for 10,000 μs (while still alternatingthe polarity of the voltage every 50 μs) and then the voltage applied tothe electrodes 1500 may decrease to 5 volts for 10000 μs (while alsostill alternating the polarity of the voltage every 50 μs).Alternatively, one or more other frequencies, voltages, and/or timeperiods may be used. This can create a 50 Hz repetition of low and highvoltage, with the high voltage periods creating an enhanced friction asan haptic effect experience by one or appendages of the operatortouching the insulating layer 1508. The greater voltage applied to theelectrodes 1500 can cause a relatively strong electrostatic effect(thus, friction enhancement) while the smaller voltage applied to theelectrodes 1500 may cause a lesser electrostatic effect (thus, smallerfriction enhancement). The alternation of these voltages can create arelatively strong haptic perception of a 50 Hz vibration or texture.Even at the lower voltage level (e.g., 5 volts), each electrode 1500 maybe charged alternately at 50 μs intervals.

FIG. 16 illustrates voltage-time curves 1600, 1602 that representvoltages applied to the electrodes 1500 (shown in FIG. 15) in accordancewith one example. The curves 1600, 1602 are shown alongside horizontalaxes 1604 representative of time and vertical axes 1606 representativeof voltage applied to the electrodes 1500. The curve 1600 represents thevoltages that are applied to the electrodes 1500 in the group or class Awhile the curve 1602 represents the voltages applied to the electrodes1500 in another group or class B. As shown in FIG. 16, the curves 1600,1602 vary over time between larger positive and negative voltages 1608,1610 and between smaller positive and negative voltages 1612, 1614. Forexample, the curves 1600, 1602 may vary between larger positive voltagesof +45 volts and larger negative voltages of −45 voltages during firsttime periods 1616 and vary between smaller positive voltages of +5 voltsand smaller negative voltages of −5 volts during second time periods1618. Alternatively, different voltages and/or waveforms of voltage maybe used than what is shown in FIG. 16. As shown in FIG. 16, the curves1600, 1602 vary such that the electrodes 1500 in the different groups orclasses are activated with opposing voltages at the same times or overthe same time periods.

The voltages applied to the electrodes 1500 can be used for sensingtouch of the insulating layer 1508 (e.g., sensing position of the fingertouching the touch surface 12), whether the voltage applied is thelarger or smaller positive and/or negative voltages (e.g., +45 volts,−45 volts, +5 volts, and/or −5 volts). When the voltage applied to anelectrode 1500 is reversed (e.g., when the appropriate curve 1600, 1602changes from a positive voltage to a negative voltage, or vice-versa),the electrode 1500 can be simultaneously discharged from both ends 1504,1506. For example, a control unit, such as the control unit 1412 shownin FIG. 14, may be conductively coupled with the ends 1504, 1506 of theelectrodes 1500 to sense the voltage that is discharged from theelectrodes 1500. If an appendage or part of an appendage of an operatoris near an electrode 1500 (such as by touching the insulating layer 1508above the electrode 1500), the appendage can form a capacitor with theelectrode 1500, as described above. As the electrode 1500 is dischargedfrom both ends 1504, 1506, more charge may flow through the end 1504 or1506 that is closer to the appendage. By comparing the amount of chargethat emerges from each end 1504, 1506, the control unit can interpolatethe position of the appendage along the electrode 1500. This axis ofappendage position may be referred to as the Y axis.

FIG. 17 illustrates one example of determining a position of anappendage 1700 engaging the insulating layer 1508 above an electrode1500 along a Y axis. In the illustrated example, the appendage 1700engages the insulating layer 1508 at a location that is approximately ⅓of the length of the electrode 1500 (e.g., from the end 1504 to theopposite end 1506 of the electrode 1500) from the end 1504 andapproximately ⅔ of the length of the electrode 1500 from the oppositeend 1506. The appendage 1700 forms a capacitive coupling with theelectrode 1500, as described above. A first portion of the charge in theelectrode 1500 from application of the voltage to the electrode 1500 isdischarged through the end 1504 while a second portion of the charge isdischarged through the end 1506. The first portion of the charge flowsthrough a first segment 1702 of the electrode 1500 that extends from theappendage 1700 to the end 1504. The second portion of the charge flowsthrough a second segment 1704 of the electrode 1500 that extends fromthe appendage 1700 to the opposite end 1506. The first segment 1702 isshorter than the second segment 1704 and, as a result, the resistance ofthe first segment 1702 may be less than the resistance of the secondsegment 1704. Consequently, the first portion of the charge that isdischarged through the first segment 1702 may be greater than the secondportion of the charge that is discharged through the second segment1704. The first and second portions of the charge may be compared inorder to identify where along the length of the electrode 1500 (e.g.,along the Y axis) that the appendage 1700 is located.

The sum total amount of charge that emerges from both ends 1504, 1506 ofthe electrode 1500 can be indicative of the amount of contact of theappendage on the electrode 1500, irrespective of the position of theappendage along Y. For example, the surface area of the interfacebetween the appendage and the insulating layer 1508 above the electrode1500 may be indicated by the sum total of the charge that emerges fromboth ends 1504, 1506. The total charge emerging from both ends 1504,1506 of several of the electrodes 1500 can be compared to spatiallylocalize one or more appendages. Each appendage covers or partiallycovers one or more of the electrodes 1500 and the charge emerging fromthese electrodes 1500 may be used to form a histogram or other discreterepresentation of a curve such as a bell curve. The position of theappendage may be identified as being at the centroid of the histogram,representation, curve, or the like. Locating the appendage or appendagesin this way perpendicular to the direction of elongation of theelectrodes 1500 may be referred to as localizing the appendage orappendages along an X axis.

FIG. 18 illustrates an appendage 1800 of an operator engaging theinsulating layer 1508 above several electrodes in a group of electrodes1500 and an accompanying histogram 1802 representative of electriccharge sensed from the electrodes 1500. The electrodes 1500 shown inFIG. 18 include the electrodes 1500A-L. The histogram 1802 includesseveral measurements 1804 (e.g., 1804A-L) that represent the chargedischarged from both ends 1504, 1506 of the corresponding electrode 1500(e.g., the measurement 1804B corresponds to the total charge from theelectrode 1500B, the measurement 1804G represents the total charge fromthe electrode 1500G, and so on).

As shown in FIG. 18, the appendage 1800 is disposed above the electrodes1500D-I and not above the electrodes 1500A-C and 1500J-L. Additionally,the surface area of the interface between the appendage 1800 and theinsulating layer 1508 above the electrodes 1500D-I (e.g., as representedby the circle associated with the reference number 1800) varies amongthe electrodes 1500D-I. For example, the amount of overlap between thissurface area of interface and the electrode 1500F is the largest of theelectrodes 1500D-I, the amount of overlap associated with the electrodes1500E and 1500G is smaller, and so on. As a result, the total chargedischarged from the electrodes 1500 may vary. As shown in the histogram1802, the distribution of charge from the electrodes 1500D-I may form acurve or approximate curve that can be used to approximately identifythe location of the appendage 1800 in the X direction, or in a directionthat is transverse to the direction of elongation of the electrodes1500. The charge from each electrode 1500D-I may correspond to theamount of overlap between the appendage 1800 and the electrode 1500 andmay be represented by the measurements 1804. For example, themeasurements 1804D-I showing larger charge may be indicative of a largersurface area of interface between the appendage 1800 and the insulatinglayer 1508 while the measurements 1804A-C and 1804J-L showing smallercharge may be indicative of a smaller or no interface between theappendage 1800 and the insulating layer 1508.

The electrodes 1500 described above may be actuated either collectivelyor individually depending on how the electronics that couples theelectrodes 1500, the control unit, and the power source(s) are arranged.In one embodiment, the electrodes 1500 of the A group or class can allbe charged to a first polarity while the electrodes 1500 of the B groupor class are all charged to an opposite second polarity. The electrodes1500 may all be charged irrespective of whether the appendage 1800 wason or near the electrodes 1500 or not. In one embodiment, the electrodes1500 can be charged via diodes, such as switching diodes, which can makeit possible to charge all of the electrodes 1500 or a group ofelectrodes 1500 at once while choosing only a single electrode 1500, ora subset of electrodes 1500 from the group, to discharge. Whileactuation is described as being performed at a level of 5 volts or 45volts depending on the sensation desired, and other voltages could alsobe used.

The measurements of touch by the appendage 1800 described above (e.g.,in the “Y direction” along the direction of elongation of the electrodesand in the “X direction” along a lateral direction across the directionof elongation of the electrodes) may be interleaved in time withactuation of the electrodes to generate haptic effects. In oneembodiment, only the positively charged electrodes were discharged fromboth ends 1504, 1506, as described above, to measure the position of theappendage. This measurement may be performed by measuring only oneelectrode at a time every 50 μs. Since the electrodes alternate inpolarity, the other electrode can be positively charge and be measured50 μs later, or at another time. If the electrodes alternate in polarityrelatively rapidly, measurements of touch by the appendage can beperformed by sweeping through the electrodes measuring just oneelectrode every 50 μs, even though all or a greater number of electrodescan be actuated every period (e.g., every 50 μs or other time period).In one embodiment, there can be 44 electrodes on a touch surface suchthat all of the electrodes can be measured for touch over a total timeperiod of 2.2 ms. Alternatively, a greater number of electrodes may bemeasured at a time and/or the measurement may occur at another rate orfrequency. Additionally or alternatively, a different number ofelectrodes may be provided.

The embodiments described above are only examples of the inventivesubject matter, and it will be evident that the principles describedabove can be extended in many ways. It may be desirable, but notessential, that the electrodes have alternating polarity spatially(e.g., neighboring electrodes have opposite polarity at a given time),as this can keep the body of the operator at a middle potential and canremove or reduce the need or effect of grounding. All or substantiallyall of the electrodes may be actuated at the same time, even when anappendage is known not to be present on some of the electrodes, or theelectrodes can be selectively actuated only when the appendage of anoperator is present in order to reduce power consumption. The electrodesdisposed under several appendages of the operator can be actuateddifferently from one another to deliver different sensation to thedifferent appendages. The frequency at which the electrodes are suppliedwith current for sensing touch can be based on whether one or moreappendages are spatially proximate to the electrodes (e.g., within adesignated distance). For example, electrodes can be charged for sensingless frequently when the electrodes are not near appendages to savepower. The electrodes can be charged to variable voltage to achievevarying effects, and not just the 5 volts and 45 volts embodimentdescribed above. The frequency of alternation between supplying thedifferent volts can be any of a variety of frequencies, not just every50 μs described above. Alternation can be desirable as such alternatingof the frequency at which the different voltages are supplied to theelectrodes can prevent or reduce diminution of electrostatic attractiondue to accumulation of surface charge.

The determination of one axis of the position of an appendage above anelectrode (e.g., along the Y direction) by use of the resistance of astripe is but one variation. For instance, each electrode may be brokenor separated into two or more segments so that the capacitance of eachsegment can be measured and used to interpolate the Y position of theappendage. Such segments may be triangles or other shapes, such asdiamond or other shapes that form a grid, such as a diamond grid.

FIG. 19 illustrates a schematic diagram of a segmented electrode 1900 inaccordance with one embodiment. In contrast to the electrodes 1500, theelectrode 1900 is divided into separate segments 1902, 1904. Theillustrated electrode 1900 is divided into elongated triangles that formthe segments 1902, 1904, but alternatively may be separated into one ormore other shapes. The capacitance of each segment 1902, 1904 may bemeasured in order to sense the touch of an operator along the length ofthe electrode 1900, similar to as described above in connection with theelectrode 1500. One difference may be that, instead of measuring thecapacitance from both ends of each segment 1902, 1904 (as is done at theends 1504, 1506 of the electrode 1500), the capacitance may be measuredat only a single end 1906, 1908 of the segments 1902, 1904. As theappendage is farther from one end 1906 or 1908 and closer to the otherend 1908 or 1906, the amount of capacitance measured from each segment1902, 1904 may differ. For example, the capacitance measured from theend 1906 of the segment 1902 may increase when the appendage touchescloser to the end 1906 and farther from the end 1908 of the othersegment 1904 while the capacitance measured from the end 1908 of thesegment 1904 decreases. Conversely, the capacitance measured from theend 1908 of the segment 1904 may increase when the appendage touchescloser to the end 1908 and farther from the end 1906 of the othersegment 1902 while the capacitance measured from the end 1906 of thesegment 1902 decreases.

As described above, the measurement of where the appendage touches abovean electrode may be performed at the transition as the electrode ischanged in polarity from a positive polarity to a negative polarity,taking only a few microseconds to perform. Measurements can also be doneon the opposite transition, from negative polarity to positive polarityand/or can be performed on both transitions. The measurement can be donefaster (e.g., less than a microsecond) or slower, forming a distinctpause between one polarity for the electrode and the other. Themeasurement can be done and then the electrode returned to a previous ororiginal potential, rather than occurring at a transition betweenpolarities. One electrode may be measured at a time, just one end of oneelectrode can be measured at a time, both ends of the electrode can bemeasured at once (as described above), many electrodes can be measuredat once, and/or all of the electrodes can be measured at one time. Oneor more, or all, of these variations can be applied to other electrodepatterns as well, for instance the segmented electrode described above.In the case of segmented electrodes having a grid of segments, the gridsegments (e.g. diamonds) can be accessed in a multiplexed way byaddressing the x and y coordinates of the segments, or the segments canbe electrically addressed individually.

ITO regions (e.g. the electrodes) for actuation and for sensing need notbe electrically connected; for instance the regions for actuation andfor sensing may alternate spatially or one be inside another, or may beon different layers.

FIG. 20 is a flowchart of one embodiment of a method 2000 for generatinghaptic effects to one or more appendages that engage a touch surface ofa touch interface device. The method 2000 may be used in conjunctionwith one or more embodiments of the device 10 described above. At 2002,one or more electrodes are positioned on, near, or within the touchsurface. For example, one or more conductive electrodes can be disposedbelow the touch surface (e.g., on a side of the surface that is oppositeof the side that is touched by an operator), within the touch surface(e.g., within the thickness of a screen), or on the touch surface (e.g.,on the same side of the surface that an operator acts to touch). Whenthe electrodes are on the touch surface, the electrodes may be disposedbeneath an insulating layer, as described above.

At 2004, the one or more electrodes are actuated to generate a hapticeffect. For example, a voltage can be applied to the electrodes so thatthe electrodes generate an electrostatic force on one or more appendagesof an operator that are engaged with the touch surface of the device.The voltage can be modulated, such as by switching the polarity of thevoltage supplied to the electrodes, as described above.

In one embodiment, the method 2000 also may include 2006, where one ormore of the electrodes are monitored to sense touch of the touch surface(e.g., the surface itself when the electrodes are below or within thesurface or the insulating layer on the electrodes when the electrodesare on the surface). As described above, the same electrodes can be usedto both generate haptic effects that are perceived by the operator ofthe device and to sense touch of the device. The electric energy (e.g.,voltage) that is supplied to the electrodes for generating hapticeffects and the electric energy that is supplied to the electrodes forsensing touch may be provided at the same time or at different times.For example, the voltage supplied for haptic actuation and the voltagesupplied for sensing touch can be provided at the same time but atdifferent frequencies to the electrodes. Alternatively, the voltagesupplied for haptic actuation and the voltage supplied for sensing touchcan be provided at different times, also as described above.

In another embodiment, a touch interface device includes a touchsurface, a first electrode, and a second electrode. The first electrodeis coupled with the touch surface and is configured to receive a firsthaptic actuation electric potential. The second electrode is coupledwith the touch surface and is configured to receive a different, secondhaptic actuation electric potential having an opposite polarity than thefirst haptic actuation potential. The first and second electrodesgenerate an electrostatic force that is imparted on one or moreappendages of an operator that touches the touch surface above both thefirst electrode and the second electrode in order to generate a hapticeffect.

In one aspect, the device also includes a control unit that configuredto modulate the polarities of the first haptic actuation electricpotential and the second haptic actuation electric potential at afrequency of at least 500 hertz. The polarities may be modulated byswitching the polarities between positive and negative values.

In one aspect, the first electrode lies across the second electrodewithout being conductively coupled with the second electrode at a firstintersection and the first and second electrodes are configured togenerate the electrostatic force on the one or more appendages thatengage the touch surface above the first intersection of the first andsecond electrodes. By “above,” it is meant that the appendage(s) engagea first side of the touch surface while the electrodes are disposed onan opposite, second side of the touch surface, regardless of which sideof the touch surface is above the other with respect to gravity.

In one aspect, the electrostatic force that is generated by the firstand second electrodes at the first intersection is greater than otherelectrostatic forces generated by the first electrode or the secondelectrode in one or more locations separated from the firstintersection.

In one aspect, the device also includes a third electrode and a fourthelectrode that are coupled with the touch surface and that areconfigured to receive third and fourth haptic actuation electricpotentials having opposite polarities, respectively. The third electrodeextends across the fourth electrode at a second intersection without thethird electrode being conductively coupled with the fourth electrode.

In one aspect, the first and second electrodes are configured togenerate the electrostatic force on a first appendage of the operatorwhen the first appendage engages the touch surface above the firstintersection of the first and second electrodes. The third and fourthelectrodes are configured to generate another, different electrostaticforce on a different, second appendage of the operator when the secondappendage concurrently engages the touch surface above the secondintersection of the third and fourth electrodes.

In one aspect, at least one of the first electrode or the secondelectrode is configured to also receive a sensing electric current inorder to sense touch of the touch surface by the one or more appendagesof the operator.

In one aspect, the at least one of the first electrode or the secondelectrode is configured to concurrently receive (a) the sensing electriccurrent and (b) the first haptic actuation electric potential or thesecond haptic actuation electric potential, respectively, to generatethe electrostatic force and concurrently sense the touch of the touchsurface by the one or more appendages.

In one aspect, the at least one of the first electrode or the secondelectrode is configured to receive the first haptic actuation electricpotential or the second haptic actuation electric potential,respectively at a first frequency and the sensing electric current at adifferent, second frequency to concurrently generate the electrostaticforce and sense the touch of the touch surface by the one or moreappendages.

In one aspect, the at least one of the first electrode or the secondelectrode is configured to receive (a) the sensing electric current and(b) the first haptic actuation electric potential or the second hapticactuation electric potential, respectively, during different timeperiods.

In one aspect, the at least one of the first electrode or the secondelectrode is elongated between opposite ends along a first direction.The device can also include a control unit configured to determine wherethe touch of the touch surface by the one or more appendages of theoperator occurs along the first direction of the at least one of thefirst electrode or the second electrode by monitoring electric chargethat is discharged from one or more of the opposite ends of the at leastone of the first electrode or the second electrode.

In one aspect, the control unit is configured to monitor the electriccharge discharged from each of the opposite ends of the at least one ofthe first electrode or the second electrode and to compare the electriccharges to determine where the touch of the touch surface by the one ormore appendages occurs along the first direction of the at least one ofthe first electrode or the second electrode.

In one aspect, the control unit is configured to monitor the electriccharges discharged from at least one of the ends of both the firstelectrode and the second electrode and to compare the electric chargesto determine where the touch of the touch surface by the one or moreappendages occurs along a different, second direction.

In one aspect, the first and second electrodes are configured to impartthe electrostatic force on the one or more appendages when the touchsurface is moving in one or more directions relative to the one or moreappendages.

In one aspect, a combination of the electrostatic force and movement ofthe touch surface generates the haptic effect. This movement may be anon-vibratory movement. For example, this movement may be one or more ofthe movements described in the '695 Application that is incorporated byreference above. The electrostatic force and the movement may create thehaptic effect on the one or appendages. This haptic effect may not beperceived by the operator (e.g., may be too small to feel or may nolonger exist) if the movement of the touch surface stops.

In one aspect, the first electrode and the second electrode areelongated conductive bodies oriented along parallel directions.

In one aspect, the first electrode and the second electrode aresufficiently small such that a finger of the operator that engages thetouch surface above the first electrode also is disposed above at leasta portion of both the second electrode.

In another embodiment, another touch interface device includes a touchsurface and elongated electrodes coupled to the touch surface. Theelectrodes include a first electrode oriented along a first directionand a second electrode oriented along a different, second direction. Thefirst electrode extends over the second electrode at a firstintersection. The first and second electrodes are configured to receivehaptic actuation electric potentials of opposite polarities to generatean electrostatic force that is imparted on the one or more appendages ofthe operator that touch the touch surface above the first intersection.

In one aspect, the device also includes a control unit configured tomodulate the polarities of the haptic actuation electric potentials.

In one aspect, the electrodes include a third electrode and a fourthelectrode with the third electrode extending across the fourth electrodeat a second intersection. The first and second electrodes are configuredto generate a first electrostatic force on a first appendage of theoperator that engages the touch surface above the first intersection.The third and fourth electrodes are configured to generate different,second electrostatic force on a different, second appendage of theoperator that concurrently engages the touch surface above the secondintersection.

In one aspect, at least one of the electrodes is configured to alsoreceive a sensing electric current in order to sense touch of the touchsurface by the one or more appendages.

In one aspect, the at least one of the electrodes is configured toconcurrently receive the haptic actuation electric potential and thesensing electric current to both generate the electrostatic force andsense the touch of the touch surface by the one or more appendages.

In one aspect, the at least one of the electrodes is configured toreceive the haptic actuation electric potential at a first frequency andthe sensing electric current at a different, second frequency tosimultaneously generate the electrostatic force and sense the touch ofthe touch surface by the one or more appendages.

In one aspect, the at least one of the electrodes is configured toreceive the haptic actuation electric potential and the sensing electriccurrent during different time periods.

In one aspect, the electrodes are elongated between opposite ends, andthe device can also include a control unit configured to determine wheretouch of the touch surface occurs along at least one of the electrodesby the one or more appendages by monitoring electric charge that isdischarged from one or more of the ends of the at least one of theelectrodes.

In one aspect, the control unit is configured to monitor the electriccharge discharged from each of the opposite ends of the at least one ofthe electrodes and to compare the electric charges to determine wherethe touch of the touch surface by the one or more appendages occursalong the at least one of the electrodes.

In one aspect, at least a subset of the electrodes are oriented parallelto each other and the device also includes a control unit configured todetermine where touch of the touch surface by the one or more appendagesoccurs laterally across the subset of the electrodes that are parallelto each other by comparing the electric charges that are discharged fromtwo or more of the electrodes in the subset.

In another embodiment, a method (e.g., for generating haptic effects ona touch surface of a touch interface device) includes applying a firsthaptic actuation electric potential having a first polarity to a firstelectrode coupled with a touch surface of a touch interface device. Themethod also includes applying a second haptic actuation electricpotential having a second polarity to a second electrode that is coupledwith the touch surface. The second polarity of the second hapticactuation potential is opposite of the first polarity of the firsthaptic actuation potential. The first and second haptic actuationpotentials generate an electrostatic force that is imparted on one ormore appendages of an operator that touch the touch surface above thefirst and second electrodes.

In one aspect, the method also includes modulating the first and secondpolarities of the first and second haptic actuation electric potentials.

In one aspect, the first electrode lies across the second electrodewithout being conductively coupled with the second electrode at a firstintersection. The first and second haptic actuation potentials generatethe electrostatic force on the one or more appendages that engage thetouch surface above the first intersection of the first and secondelectrodes.

In one aspect, the electrostatic force that is generated by the firstand second haptic actuation potentials at the first intersection isgreater than other electrostatic forces generated by the first electrodeor the second electrode in one or more locations separated from thefirst intersection.

In one aspect, the method also includes applying a third hapticactuation potential to a third electrode that is coupled to the touchsurface and applying a fourth haptic actuation potential to a fourthelectrode that is coupled to the touch surface. The third and fourthhaptic actuation potentials have opposite polarities. The firstelectrode extends across the second electrode at a first intersectionwithout being conductively coupled with the second electrode and thethird electrode extends across the fourth electrode at a secondintersection without the third electrode being conductively coupled withthe fourth electrode.

In one aspect, the first and second haptic actuation potentials that areapplied to the first and second electrodes generate a firstelectrostatic force on a first appendage of the operator that touchesthe touch surface above the first intersection. The third and fourthhaptic actuation potentials that are applied to the third and fourthelectrodes generate a different, second electrostatic force on adifferent, second appendage of the operator when the second appendageconcurrently engages the touch surface above the second intersection.

In one aspect, the method also includes applying a sensing electriccurrent to the first electrode in order to sense touch of the touchsurface by the one or more appendages.

In one aspect, applying the first haptic actuation electric potentialoccurs at a first frequency and applying the sensing electric current tothe first electrode occurs at a different, second frequency toconcurrently generate the electrostatic force and sense the touch of thetouch surface by the one or more appendages using the first electrode.

In one aspect, applying the first haptic actuation electric potentialand applying the sensing electric current occur during different timeperiods.

In one aspect, the at least one of the first electrode or the secondelectrode is elongated between opposite ends along a first direction.The method can also include determining where the touch of the touchsurface by the one or more appendages of the operator occurs along theat least one of the first electrode or the second electrode bymonitoring electric charge that is discharged from one or more of theopposite ends of the at least one of the first electrode or the secondelectrode.

In one aspect, the method also includes monitoring the electric chargedischarged from each of the opposite ends of the at least one of thefirst electrode or the second electrode and comparing the electriccharges to determine where the touch of the touch surface by the one ormore appendages occurs along the at least one of the first electrode orthe second electrode.

In one aspect, the method also includes monitoring the electric chargesdischarged from at least one of the ends of both the first electrode andthe second electrode and comparing the electric charges to determinewhere the touch of the touch surface by the one or more appendagesoccurs along a different, second direction.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventivesubject matter described herein without departing from its scope. Whilethe dimensions and types of materials described herein are intended todefine the parameters of the inventive subject matter, they are by nomeans limiting and are exemplary embodiments. Many other embodimentswill be apparent to one of ordinary skill in the art upon reviewing theabove description. The scope of the subject matter described hereinshould, therefore, be determined with reference to the appended claims,along with the full scope of equivalents to which such claims areentitled. In the appended claims, the terms “including” and “in which”are used as the plain-English equivalents of the respective terms“comprising” and “wherein.”Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to impose numerical requirements on their objects. Further,the limitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. §112, sixth paragraph, unless and until such claimlimitations expressly use the phrase “means for” followed by a statementof function void of further structure.

This written description uses examples to disclose several embodimentsof the inventive subject matter and also to enable any person ofordinary skill in the art to practice the embodiments disclosed herein,including making and using any devices or systems and performing anyincorporated methods. The patentable scope of the subject matter isdefined by the claims, and may include other examples that occur to oneof ordinary skill in the art. Such other examples are intended to bewithin the scope of the claims if they have structural elements that donot differ from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

The foregoing description of certain embodiments of the disclosedsubject matter will be better understood when read in conjunction withthe appended drawings. To the extent that the figures illustratediagrams of the functional blocks of various embodiments, the functionalblocks are not necessarily indicative of the division between hardwarecircuitry. Thus, for example, one or more of the functional blocks (forexample, processors or memories) may be implemented in a single piece ofhardware (for example, a general purpose signal processor,microcontroller, random access memory, hard disk, and the like).Similarly, the programs may be stand alone programs, may be incorporatedas subroutines in an operating system, may be functions in an installedsoftware package, and the like. The various embodiments are not limitedto the arrangements and instrumentality shown in the drawings.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of the presently describedinventive subject matter are not intended to be interpreted as excludingthe existence of additional embodiments that also incorporate therecited features. Moreover, unless explicitly stated to the contrary,embodiments “comprising,” “including,” or “having” an element or aplurality of elements having a particular property may includeadditional such elements not having that property.

Since certain changes may be made in the above-described systems andmethods, without departing from the spirit and scope of the subjectmatter herein involved, it is intended that all of the subject matter ofthe above description or shown in the accompanying drawings shall beinterpreted merely as examples illustrating the inventive conceptsherein and shall not be construed as limiting the disclosed subjectmatter.

What is claimed is:
 1. A touch interface device comprising: a touchsurface; a first electrode coupled with the touch surface, the firstelectrode also configured to receive a first actuation electricpotential; and a second electrode coupled with the touch surface andconfigured to receive a second actuation electric potential differentfrom the first actuation electric potential wherein when an appendage ofan operator touches the touch surface above both the first electrode andthe second electrode the first and second actuation electric potentialsestablish electric fields that pass from one of the first and secondelectrodes directly through the outermost layer of the appendage andreturn to the other of the first and second electrodes via the outermostlayer of the appendage, wherein electric fields that penetrate theoutermost layer of the appendage are small enough that they do notcreate direct electric sensory stimulation, and wherein the electricfields acting on the outermost layer of the appendage generateelectrostatic attractive forces that are imparted directly on theappendage and increase friction between the touch surface and theappendage through which the electric fields pass.
 2. The device of claim1, further comprising a control unit configured to modulate thepolarities of the first actuation electric potential and the secondactuation electric potential with respect to a ground potential at afrequency of at least 500 hertz.
 3. The device of claim 1, wherein thefirst electrode lies across the second electrode without beingconductively coupled with the second electrode at a first intersection,and the first and second electrodes are configured to generate theelectrostatic attractive forces on the appendage that touches the touchsurf ace above the first intersection of the first and secondelectrodes.
 4. The device of claim 3, wherein the electrostaticattractive forces that are generated by the first and second electrodesat the first intersection are greater than other electrostatic forcesgenerated by the first electrode or the second electrode in one or morelocations separated from the first intersection.
 5. The device of claim3, further comprising a third electrode and a fourth electrode coupledwith the touch surface and configured to receive third and fourthactuation electric potentials in which the third potential is differentfrom the fourth potential, wherein the third electrode extends acrossthe fourth electrode at a second intersection without the thirdelectrode being conductively coupled with the fourth electrode.
 6. Thedevice of claim 5, wherein the first and second electrodes areconfigured to generate the electrostatic attractive forces on a firstappendage of the operator when the first appendage touches the touchsurf ace above the first intersection of the first and secondelectrodes, and wherein the third and fourth electrodes are configuredto generate other, different electrostatic attractive forces on adifferent, second appendage of the operator when the second appendageconcurrently engages the touch surface above the second intersection ofthe third and fourth electrodes.
 7. The device of claim 1, wherein atleast one of the first electrode or the second electrode is configuredto also receive a sensing electric current in order to sense touch ofthe touch surf ace by the appendage of the operator.
 8. The device ofclaim 7, wherein the at least one of the first electrode or the secondelectrode is configured to concurrently receive (a) the sensing electriccurrent and (b) the first actuation electric potential or the secondactuation electric potential, respectively, to generate theelectrostatic attractive forces and concurrently sense the touch of thetouch surface by the appendage.
 9. The device of claim 8, wherein the atleast one of the first electrode or the second electrode is configuredto receive the first actuation electric potential or the secondactuation electric potential, respectively at a first frequency and thesensing electric current at a different, second frequency toconcurrently generate the electrostatic attractive forces and sense thetouch of the touch surface by the appendage.
 10. The device of claim 7,wherein the at least one of the first electrode or the second electrodeis configured to receive (a) the sensing electric current and (b) thefirst actuation electric potential or the second electric potential,respectively, during different time periods.
 11. The device of claim 7,wherein the at least one of the first electrode or the second electrodeis elongated between opposite ends along a first direction, and furthercomprising a control unit configured to determine where the touch of thetouch surface by the appendage of the operator occurs along the firstdirection of the at least one of the first electrode or the secondelectrode by monitoring electric charge that is discharged from one ormore of the opposite ends of the at least one of the first electrode orthe second electrode.
 12. The device of claim 11, wherein the controlunit is configured to monitor the electric charge discharged from eachof the opposite ends of the at least one of the first electrode or thesecond electrode and to compare the electric charges to determine wherethe touch of the touch surf ace by the appendage occurs along the firstdirection of the at least one of the first electrode or the secondelectrode.
 13. The device of claim 11, wherein the control unit isconfigured to monitor the electric charges discharged from at least oneof the ends of both the first electrode and the second electrode and tocompare the electric charges to determine where the touch of the touchsurf ace by the appendage occurs along a different, second direction.14. The device of claim 1, wherein the first and second electrodes areconfigured to impart the electrostatic attractive forces on theappendage when the touch surface is moving in one or more directionsrelative to the appendage.
 15. The device of claim 14, wherein acombination of the electrostatic attractive forces and movement of thetouch surface generates a haptic effect.
 16. The device of claim 1,wherein the first electrode and the second electrode are elongatedconductive bodies oriented along parallel directions.
 17. The device ofclaim 1, wherein the first electrode and the second electrode aresufficiently small such that when the appendage is a finger of theoperator that touches the touch surface above the first electrode, thefinger also is disposed above at least a portion of the secondelectrode.
 18. A touch interface device comprising: a touch surface; andelongated electrodes coupled with the touch surf ace and configured tobe disposed beneath an insulating layer, the electrodes including afirst electrode oriented along a first direction and a second electrodeoriented along a different, second direction, the first electrodeextending over the second electrode at a first intersection, wherein thefirst and second electrodes are configured to receive actuation electricpotentials that are different from one another, and wherein when anappendage of an operator touches the touch surface above the firstintersection the actuation electric potentials establish electric fieldsthat pass from one of the first and second electrodes directly throughthe outermost layer of the appendage and return to the other of thefirst and second electrodes via the outermost layer of the appendage,wherein electric fields that penetrate the outermost layer of theappendage are small enough that they do not create direct electricsensory stimulation, and wherein the electric fields acting on theoutermost layer of the appendage generate electrostatic attractiveforces that are imparted directly on the appendage and increase frictionbetween the touch surface and the appendage through which the electricfields pass.
 19. The device of claim 18, further comprising a controlunit configured to modulate the polarities of the actuation electricpotentials with respect to a ground potential.
 20. The device of claim19, wherein at least one of the electrodes is configured to also receivea sensing electric current in order to sense touch of the touch surfaceby the appendage.
 21. The device of claim 20, wherein the at least oneof the electrodes is configured to concurrently receive the actuationelectric potential and the sensing electric current to both generate theelectrostatic attractive forces and sense the touch of the touch surfaceby the appendage.
 22. The device of claim 21, wherein the at least oneof the electrodes is configured to receive the actuation electricpotential at a first frequency and the sensing electric current at adifferent, second frequency to simultaneously generate the electrostaticattractive forces and sense the touch of the touch surface by theappendage.
 23. The device of claim 20, wherein the at least one of theelectrodes is configured to receive the actuation electric potential andthe sensing electric current during different time periods.
 24. Thedevice of claim 18, wherein the elongated electrodes include a thirdelectrode and a fourth electrode with the third electrode extendingacross the fourth electrode at a second intersection, and wherein thefirst and second electrodes are configured to generate firstelectrostatic attractive forces on a first appendage of the operatorthat engages the touch surf ace above the first intersection, andwherein the third and fourth electrodes are configured to generatedifferent, second electrostatic attractive forces on a different, secondappendage of the operator that concurrently engages the touch surfaceabove the second intersection.
 25. The device of claim 18, wherein theelectrodes are elongated between opposite ends, and further comprising acontrol unit configured to determine where touch of the touch surfaceoccurs along at least one of the electrodes by the appendage bymonitoring electric charge that is discharged from one or more of theends of the at least one of the electrodes.
 26. The device of claim 25,wherein the control unit is configured to monitor the electric chargedischarged from each of the opposite ends of the at least one of theelectrodes and to compare the electric charges to determine where thetouch of the touch surf ace by the appendage occurs along the at leastone of the electrodes.
 27. The device of claim 18, wherein at least asubset of the electrodes are oriented parallel to each other, andfurther comprising a control unit configured to determine where touch ofthe touch surface by the appendage occurs laterally across the subset ofthe electrodes that are parallel to each other by comparing the electriccharges that are discharged from two or more of the electrodes in thesubset.
 28. A method comprising: applying a first actuation electricpotential having a first polarity to a first electrode coupled with atouch surface of a touch interface device; and applying a secondactuation electric potential having a second polarity to a secondelectrode that is coupled with the touch surface, the second polarity ofthe second actuation potential being opposite of the first polarity ofthe first actuation potential with respect to a ground potential,wherein when an appendage of an operator touches the touch surface abovethe first intersection the actuation electric potentials establishelectric fields that pass from one of the first and second electrodesdirectly through the outermost layer of the appendage and return to theother of the first and second electrodes via the outermost layer of theappendage, wherein electric fields that penetrate the outermost layer ofthe appendage are small enough that they do not create direct electricsensory stimulation, and wherein the electric fields acting on theoutermost layer of the appendage generate electrostatic attractiveforces that are imparted directly on the appendage and increase frictionbetween the touch surface and the appendage through which the electricfields pass.
 29. The method of claim 28, further comprising modulatingthe polarities of the first and second actuation electric potentialswith respect to a ground potential.
 30. The method of claim 28, whereinthe first electrode lies across the second electrode without beingconductively coupled with the second electrode at a first intersection,and the first and second actuation potentials generate the electrostaticattractive forces on the appendage that touch the touch surface abovethe first intersection of the first and second electrodes.
 31. Themethod of claim 30, wherein the electrostatic attractive forces that aregenerated by the first and second actuation potentials at the firstintersection are greater than other electrostatic forces generated bythe first electrode or the second electrode in one or more locationsseparated from the first intersection.
 32. The method of claim 28,further comprising: applying a third actuation potential to a thirdelectrode that is coupled to the touch surface; and applying a fourthactuation potential to a fourth electrode that is coupled to the touchsurface, the third and fourth actuation potentials being different fromone another, wherein the first electrode extends across the secondelectrode at a first intersection beneath the touch surface withoutbeing conductively coupled with the second electrode and the thirdelectrode extends across the fourth electrode at a second intersectionbeneath the touch surface without the third electrode being conductivelycoupled with the fourth electrode.
 33. The method of claim 32, whereinthe first and second actuation potentials that are applied to the firstand second electrodes generate first electrostatic attractive forces ona first appendage of the operator that touches the touch surface abovethe first intersection, and wherein the third and fourth actuationpotentials that are applied to the third and fourth electrodes generatedifferent, second attractive forces on a different, second appendage ofthe one or more appendages of the operator when the second appendageconcurrently touches the touch surface above the second intersection.34. The method of claim 33, wherein applying the first actuationelectric potential and applying the sensing electric current occurduring different time periods.
 35. The method of claim 33, wherein theat least one of the first electrode or the second electrode is elongatedbetween opposite ends along a first direction, and further comprisingdetermining where the touch of the touch surf ace by the appendage ofthe operator occurs along the at least one of the first electrode or thesecond electrode by monitoring electric charge that is discharged fromone or more of the opposite ends of the at least one of the firstelectrode or the second electrode.
 36. The method of claim 35, furthercomprising monitoring the electric charge discharged from each of theopposite ends of the at least one of the first electrode or the secondelectrode and comparing the electric charges to determine where thetouch of the touch surface by the appendage occurs along the at leastone of the first electrode or the second electrode.
 37. The method ofclaim 35, further comprising monitoring the electric charges dischargedfrom at least one of the ends of both the first electrode and the secondelectrode and comparing the electric charges to determine where thetouch of the touch surf ace by the appendage occurs along a different,second direction.
 38. The method of claim 28, further comprisingapplying a sensing electric current to the first electrode in order tosense touch of the touch surf ace by the appendage.
 39. The method ofclaim 38, wherein applying the first actuation electric potential occursat a first frequency and applying the sensing electric current to thefirst electrode occurs at a different, second frequency to concurrentlygenerate the electrostatic attractive forces and sense the touch of thetouch surface by the appendage using the first electrode.